全新java初学者实践教程6(Java SE5.0版)
Zj ^e8u=T 基本语法3
xmC5uT6L3M jHatUez4O b{-|q6 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
\21Gg%W5AE LqJV [font="Times] 1.循环语句[font="Times]:while,do-while,for
FS @55mQ @t$yg$Q?[ [font="Times]2.分支语句[font="Times]:if-else,switch,
gPd, [font="Times]
if\`M'3Xx 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
){,Mv:#+T [font="Times]
w}$;2g0=a< 4.异常处理语句[font="Times]:try-catch-finally,throw
FrLv%tK| UEYJd&n0CB 实践:
C; U4`0=8 [font="Times] 1.循环语句
awz.~c++ [font="Times] while 语句
7)RvBcM [font="Times]class While {
OuWRLcJ! [font="Times]public static void main(String args[]) {
ScVbo3{m*T [font="Times]int n = 10;
j!k$SDA- [font="Times]while(n > 0) {
Nqd9)WQ [font="Times]System.out.println("tick " + n);
+`B^D [font="Times]n--;
KE5>O1 [font="Times]}
xc`O\z_) [font="Times]}
M80O;0N%A [font="Times]}
7aPA+gA/ [font="Times] do…while 语句
c3PA<q[ [font="Times] class DoWhile {
<)sL8G9Y [font="Times]public static void main(String args[]) {
*(]ZdB_2 [font="Times]int n = 10;
`}$bJCSF.n [font="Times]do {
oGg<s3;UND [font="Times]System.out.println("tick " + n);
]EDCs?, [font="Times]n--;
L
9cXgd [font="Times]} while(n > 0);
mC0Dj O [font="Times]}
i$6a0'@U [font="Times]}
P&tw!B 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
*a{WJbau] [font="Times] for语句
tBl(E [font="Times] class ForTick {
^x^(Rk}| [font="Times]public static void main(String args[]) {
l)jP!k [font="Times]int n;
f$dIPt( [font="Times]for(n=10; n>0; n--)
fWs*u[S [font="Times]System.out.println("tick " + n);
)_o^d>$da [font="Times]}
4N7|LxNNl_ [font="Times]}
akCCpnX_d 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
swJQwY 还有啊,[font="Times]for循环的部分可以为空的
Y;g\ @j [font="Times]class ForVar {
o:4#AkS [font="Times]public static void main(String args[]) {
_E6N*ORV [font="Times]int i;
zq ?xY`E [font="Times]boolean done = false;
8$X3 J[_j [font="Times]i = 0;
10m|? [font="Times]for( ; !done; ) {
2 1+[9 [font="Times]System.out.println("i is " + i);
Q~' \oWz [font="Times]if(i == 10) done = true;
UYW'pV [font="Times]i++;
e$`hRZ%
[font="Times]}
plJUQk [font="Times]}
r/P}j4)b7 [font="Times]}
循环语句的例子下载 `@0AGSzUv [font="Times] 2.分支语句[font="Times]
}&6:0l$4! [font="Times] if/else语句
hK{<&T [font="Times]class IfElse {
fuF{8-ua [font="Times]public static void main(String args[]) {
rp[3?-fk [font="Times]int month = 4; // April
QX=x^(M$m [font="Times]String season;
yO7#n0q [font="Times]if(month == 12 || month == 1 || month == 2)
:c8d([)$ [font="Times]season = "Winter";
Z^_zcH' [font="Times]else if(month == 3 || month == 4 || month == 5)
,]n~j-X [font="Times]season = "Spring";
0&2`)W?9 [font="Times]else if(month == 6 || month == 7 || month == 8)
%yl17:h# [font="Times]season = "Summer";
A
McZm0c` [font="Times]else if(month == 9 || month == 10 || month == 11)
a <F2]H=J [font="Times]season = "Autumn";
0B}2~}# [font="Times]else
"o_'q@.} [font="Times]season = "Bogus Month";
AA=eWg [font="Times]System.out.println("April is in the " + season + ".");
|~18MW [font="Times]}
AUIp
vd
[font="Times]}
WNKP';(a@G [font="Times]//这段程序输出[font="Times]:
8`]yp7ueS [font="Times]//April is in the Spring.
DpT$19Q+ [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
i*!2n1c[ [font="Times] switch语句
B/!/2x [font="Times] class Switch {
)DlKeiK [font="Times]public static void main(String args[]) {
fYh<S [font="Times]int month = 4;
N&Ho$,2s [font="Times]String season;
Unb3
Gv#O [font="Times]switch (month) {
rQ U6*f [font="Times]case 12:
%9S0!h\ [font="Times]case 1:
QH,(iX6RY [font="Times]case 2:
o?a3hD [font="Times]season = "Winter";
"QiLu=Rq [font="Times]break;
YB2gxZ [font="Times]case 3:
x#R6Ez7 [font="Times]case 4:
?0+g.,9 [font="Times]case 5:
e:C4f [font="Times]season = "Spring";
&,{YfAxQ` [font="Times]break;
{[L('MH2| [font="Times]case 6:
\ a(ce?C [font="Times]case 7:
3 5L0CM [font="Times]case 8:
(-&d0a9N [font="Times]season = "Summer";
hv\Dz*XTs0 [font="Times]break;
Y|
ch ; [font="Times]case 9:
<l5m\A [font="Times]case 10:
Cz9MXb]B [font="Times]case 11:
3hUP>F8 [font="Times]season = "Autumn";
VRD^> Gi [font="Times]break;
MHye!T6fO\ [font="Times]default:
2\gIjXX" [font="Times]season = "Bogus Month";
?N!kYTR%} [font="Times]}
~#}T| [font="Times]System.out.println("April is in the " + season + ".");
b`=g#B| [font="Times]}
6qT- [font="Times]}
分支语句代码下载 WLfDXx2A ae]6F_Qtc* [font="Times]switch语句适合于条件非常多的逻辑
d~{$,"!-f 请看上述语句可以混合使用,请看
下载例子